Method and device for treating edges in a high pressure fuel accumulator

ABSTRACT

A method and an apparatus for edge shaping in a high-pressure fuel reservoir which has an elongated tubular casing element equipped in the longitudinal direction with a continuous recess which forms the interior space of the high-pressure fuel reservoir and is open at at least one end, the recess opening into at least one passthrough orifice, that together with the continuous recess forms a peripheral edge. An elongated actuation element, whose end inserted into the continuous recess is equipped with a surface segment inclined with respect to the longitudinal axis of the continuous recess, is inserted into the continuous recess, the surface segment acting at least indirectly on a pressure element introduced into the continuous recess so that a surface portion of the pressure element is pressed against the peripheral edge, and a smoothing of the edge contour is achieved because of a material displacement in the region of the edge.

FIELD OF THE INTERVIEW

[0001] The present invention relates to a method and an apparatus foredge shaping in a high-pressure fuel reservoir.

BACKGROUND INFORMATION

[0002] A high-pressure fuel reservoir for a fuel injection system forinternal combustion engines is presented, for example, in GermanPublished Patent Application No. 196 40 480. This reference discloses anelongated tubular casing element made of steel which can be connected toa high-pressure fuel pump. The casing element has a continuous recesswhich extends in the longitudinal direction, constitutes the interiorspace of the high-pressure fuel reservoir, and is open at at least oneend. When the high-pressure fuel reservoir is in the completelyinstalled state, the at least one open end is closed off by theconnector of the high-pressure fuel pump or of a pressure-limitingvalve, or in another manner. The fuel contained in the high-pressurefuel reservoir and impinged upon by high pressure is delivered, viamultiple connectors configured in the casing element and high-pressurelines connected thereto, to electrically controlled injection valves(called “injectors”) for injection into the combustion chambers of acompression-ignited internal combustion engine. A high-pressure fuelreservoir of this kind is also called a “common rail.” The connectors ofthe high-pressure fuel reservoir are configured in the form of connectorfittings which stand out from the casing element and are each equippedwith a passthrough orifice, configured as a bore, that opens into thecontinuous recess of the casing element. The passthrough orifice forms aperipheral edge with the continuous recess. As a result of the highinternal pressure (approximately 1350 bar) in the high-pressure fuelreservoir and because of the narrow diameter (a few millimeters) of thebores, abrasive particles in the fuel cause wear phenomena in the regionof the peripheral edge formed by the passthrough orifice and the innerwall of the continuous recess. For this reason, it is desirable to roundoff or smooth the edge contour. It is known to shape and round off theedge contour using methods such as, for example, honing, in which anabrasive paste is used. These methods are, however, relativelycumbersome and very complex.

SUMMARY OF THE INVENTION

[0003] The method according to the present invention makes it possibleto greatly reduce the effort necessary for smoothing the edge contour.The method can be performed very economically and inexpensively, anduses a pressure element that is pressed, by an actuation elementintroduced into the continuous recess, against the peripheral edge insuch a way that smoothing of the edge contour is achieved by materialdisplacement in the region of the edge. The modification of the edgecontour advantageously contributes to an increase in material strength.As a result, cracks, fractures, and particle detachments occur much lessfrequently on the rounded edge that has been consolidated with respectto the fuel flow.

[0004] It is furthermore advantageous if a guide element, in which thepressure element is mounted movably perpendicularly to the longitudinalaxis of the continuous recess, is used to guide the pressure element.Using the guide element, a force acting on the actuation element in theinsertion direction of the actuation element is deflected in enhancedfashion perpendicularly to the longitudinal axis of the continuousrecess, and acts substantially in that direction on the edge of thehigh-pressure fuel reservoir that is to be shaped.

[0005] Advantageously, the guide element is initially arranged shiftablyin the continuous recess, so that upon contact by the pressure elementagainst the peripheral edge, the guide element is shifted in thecontinuous recess until the pressure element is arranged centeredly withrespect to the continuous recess. The guide element can then beimmobilized with respect to the high-pressure fuel reservoir, and theedge contour can be shaped by pressure of the pressure element.

[0006] It is particularly advantageous if a ball whose diameter isgreater than the inside diameter of the passthrough orifice is used asthe pressure element. A ball is particularly easy to manufacture withthe necessary precision and possesses great mechanical stability, sothat a ball is particularly suitable as a pressure element. Thespherical shape of the ball surface is particularly suitable for shapingthe edge contour.

[0007] Any drilling burr that may be present on the edge formed by thecontinuous recess and the passthrough orifice is advantageously removedbefore the pressure element is pressed on, since the presence of adrilling burr can greatly impair smoothing of the edge contour. Themethod described in German Published Patent Application No. 100 01 507,for example, can be used to remove a burr.

[0008] Also provided is an apparatus for edge shaping in a high-pressurefuel reservoir which has an elongated tubular casing element that isequipped in the longitudinal direction with a continuous recess whichforms the interior space of the high-pressure fuel reservoir and is openat at least one end. The at least one end opens into at least onepassthrough orifice, configured as a bore, that with the continuousrecess forms a peripheral edge. The apparatus includes: an elongatedcasing-shaped guide element that is insertable into the continuousrecess, having a recess extending in the longitudinal direction of theguide element and an orifice branching off from the recessperpendicularly to the longitudinal direction; a pressure elementmounted movably in the orifice; and an actuation element. The actuationelement acts with the pressure element and is arranged shiftably in therecess, and is equipped at its end inserted into the recess with asurface segment that is inclined at an angle with respect to thelongitudinal direction of the guide element and is in contact againstthe pressure element. In this context, the pressure element can, byintroduction of the actuation element into the guide element, beimpinged upon by a force, and consequently push out with a surfaceportion through the orifice of the guide element in order to shape theedge of the high-pressure fuel reservoir.

[0009] Advantageously, the actuation element is arranged in slidinglyshiftable fashion in the recess of the guide element, and is ofwedge-shaped configuration at its end inserted into the recess.

[0010] The orifice in the casing-shaped guide element can be configuredsimply as a radial bore.

[0011] It is particularly advantageous if the pressure element makescontact against the inner wall of the orifice with a slight lateralclearance. This results in accurate guidance of the pressure element.The pressure element can advantageously be configured as a ball. Thediameter of the ball is greater than the inside diameter of thepassthrough orifice.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 shows a cross-section, depicted in simplified fashion,through a high-pressure fuel reservoir having connector fittings and aninserted apparatus for edge shaping.

[0013]FIG. 2 shows the cross section of FIG. 1 at a later phase ofshaping.

[0014]FIG. 3 shows the cross section of FIG. 1 as the ball pressesagainst a peripheral edge of the high-pressure fuel reservoir.

[0015]FIGS. 4a and 4 b show enlarged detail views of the edge contourduring shaping with the pressure element.

DETAILED DESCRIPTION

[0016]FIG. 1 depicts a cross section through a high-pressure fuelreservoir that encompasses an elongated tubular casing element 1 made ofmetal which has, in order to supply fuel injection valves, shaped-onconnector fittings 3 which are produced, for example, by forging.Further connector fittings 3 which serve to connect to a high-pressurefuel pump or a pressure sensor can, of course, also be provided. Theinterior space of the high-pressure fuel reservoir is formed by acontinuous recess 2, extending in the longitudinal direction of casingelement 1, which may have a circular cross section, for example.Continuous recess 2 constituted in casing element 1 can be permanentlyclosed off at one end. The other end is open and can be closed off, forexample, with a screwed-on pressure relief valve, the connector to thehigh-pressure fuel pump, a cover, or in another manner. Continuousrecess 2 forms a peripheral edge 7 together with each of passthroughorifices 5.

[0017] Any drilling burr that may be present on peripheral edge 7 isfirst removed before the edge contour of edge 7 is smoothed. This can bedone, for example, in the manner described in German Patent ApplicationNo. 100 01 507.

[0018] As also depicted in FIG. 1, a shaping apparatus is introducedinto continuous recess 2 from the open end of the high-pressure fuelreservoir. This apparatus encompasses an elongated, casing-shaped guideelement 11. Guide element 11 can, for example, be a tube having adiameter that is somewhat smaller than inside diameter a of thehigh-pressure fuel reservoir, so that the guide element can be easilyintroduced into continuous recess 2. In the example shown here, insidediameter a of the high-pressure fuel reservoir is 11 mm. Diameter d ofthe passthrough orifice is 3.5 mm. The longitudinal axis of guideelement 11 coincides with longitudinal axis 6 of the high-pressure fuelreservoir. The guide element has a cylindrical recess 12 with a diameterof 7 mm, extending in the longitudinal direction of the guide element,in which a rod-like actuation element 13 is arranged in slidinglyshiftable fashion. The end of actuation element 13 introduced intorecess 12 is of wedge-shaped configuration, with a surface segment 14that is inclined with respect to the longitudinal direction of guideelement 11 at an angle α which is less than 45°. In the depictedembodiment, the angle is 15°. In addition, an orifice 16 branches offfrom recess 12 perpendicularly to the longitudinal axis of guide element11. Orifice 16 can be created in guide element 11 as, for example, aradial bore. A pressure element configured as ball 10 is mounted inorifice 16 movably in a direction y perpendicular to the longitudinaldirection of guide element 11. The diameter of the ball is selected tobe slightly smaller than the inside diameter of orifice 16, so that theball is guided by the inner wall of orifice 16 with a slight lateralclearance. In the exemplary embodiment shown here, the diameter of ball10 is approximately 5 mm. The ball is produced from a particularly hardmaterial that is harder than the material of the high-pressure fuelreservoir. Ball 10 cooperates with inclined surface segment 14 ofactuation element 13 as depicted in FIGS. 1 through 3.

[0019] Upon insertion of guide element 11, actuation element 12 isinitially in the position indicated with dashed lines as P1 in FIG. 1.Ball 10 rests against the inner wall of orifice 16 and against inclinedsurface segment 14 of actuation element 13. In position P1, a surfaceportion 10 a of the ball located opposite inclined surface segment 14 isarranged in recessed fashion (not depicted) inside orifice 16, so thatthe apparatus can be introduced without difficulty into continuousrecess 2. Guide element 11 is brought into a position in which orifice16 is arranged approximately coaxially with passthrough orifice 5 of thehigh-pressure fuel reservoir.

[0020] Actuation element 13 is inserted in direction x farther intorecess 12, to position P2. One end (not depicted) of actuation element13 that protrudes from the guide device serves as a handle duringinsertion of actuation element 13. As actuation element 13 is inserted,ball 10 slides along inclined surface segment 14 and is moved indirection y in orifice 16, perpendicularly to the longitudinal directionof guide element 11, into the position depicted in FIG. 1. Furtherinsertion of actuation element 13 over a distance of a few millimeters,into position P3 shown in FIG. 2, causes the ball to be moved farther inthe y direction along the inner wall of orifice 16 until a segment ofthe ball projects out of orifice 16 and, at surface portion 10 a, comesinto contact against edge 7 of the high-pressure fuel reservoir. As soonas the first contact with edge 7 is made, a further advance of ball inthe y direction results in a shifting of guide element 11 (which in thisphase is freely movable and slidingly shiftable) in continuous recess 2,until ball 10 is in contact against two opposite points of peripheraledge 7 and is centered with respect to passthrough orifice 5. Guideelement can then be immobilized so that it cannot be shifted further byball 10 in its position relative to high-pressure fuel reservoir 1.

[0021] The next step is shown in FIG. 3. Pressure on actuation element13 causes the latter to move into position P4. In this example, theentire displacement travel from position P1 to position P4 is onlyapproximately 5 mm. Ball 10 is moved farther in direction y. Because ofthe inner wall of orifice 16 of guide element 11, the force transferredfrom inclined surface segment 14 to ball 10 is deflected substantiallyinto the y direction, since the force components perpendicular to the ydirection are compensated for by the immobilized guide element 11. Inprinciple, however, it is also possible to perform the method withoutguide element 11 and to use only actuation element 13 and ball 10, sincethe actuation element and ball can in a certain respect be wedged incontinuous recess 2 when the ball is in contact against edge 7. The useof a guide element is advantageous, however, since it not only greatlyfacilitates handling but also can optimize the application of force ontoedge 7.

[0022] As ball 10 is pressed against edge 7, material displacementcauses the edge contour to be modified. This is depicted in enlargedfashion in FIGS. 4a and 4 b. The manner in which edge 7 is smoothed orrounded off by the pressure of ball 10 and the resulting materialdisplacement is evident from FIG. 4b.

[0023] Peripheral edge 7 formed by the cylindrical continuous recess 2and cylindrical passthrough orifice 5 does not lie in one plane, and iscurved in three dimensions. As ball 10 is pressed on, it thereforeinitially comes into contact only at two opposite points on peripheraledge 7. With further pressure, ball 10 also comes into contact atadditional points on the peripheral edge, so that these also can beshaped. A consequence of this is that not all points on the edge contourare uniformly shaped, since the ball is pressed more strongly into theedge at those points where it comes into contact first than at thosepoints where it comes into contact last. Satisfactory smoothing over theentire extent of the edge can nevertheless be achieved with the methodset forth above.

What is claimed is:
 1. A method for edge shaping in a high-pressure fuelreservoir which has an elongated tubular casing element (1) that isequipped in the longitudinal direction with a continuous recess (2),which forms the interior space of the high-pressure fuel reservoir andis open at at least one end, into which opens at least one passthroughorifice (5), configured as a bore, that together with the continuousrecess (2) forms a peripheral edge (7), wherein an elongated actuationelement (13), whose end inserted into the continuous recess (2) isequipped with a surface segment (14) that is inclined with respect tothe longitudinal axis (6) of the continuous recess (2), is inserted intothe continuous recess (2), which surface segment acts at leastindirectly on a pressure element (10) introduced into the continuousrecess (2) in such a way that a surface portion (10 a) of the pressureelement (10) is pressed against the peripheral edge (7), and a smoothingof the edge contour is achieved because of a material displacementresulting therefrom in the region of the edge (7).
 2. The method asdefined in claim 1, wherein a guide element (11), in which the pressureelement (10) is mounted movably perpendicularly to the longitudinal axis(6) of the continuous recess (2), is used to guide the pressure element.3. The method as defined in claim 2, wherein a force acting on theactuation element (13) in the insertion direction (x) of the actuationelement is deflected perpendicularly to the longitudinal axis (6) of thecontinuous recess by the inclined surface segment (14), the pressureelement (10), and the guide element (11), and acts substantially in thatdirection (y) on the edge contour (7) of the high-pressure fuelreservoir (1).
 4. The method as defined in claim 2, wherein the guideelement (11) is arranged shiftably in the continuous recess (2), andupon contact by the pressure element (10) against the peripheral edge(7) is shifted in the continuous recess (2) until the pressure element(10) is arranged centeredly with respect to the passthrough orifice (5).5. The method as defined in claim 4, wherein after the centeringoperation of the pressure element (10), the initially freely shiftableguide element (11) is immobilized.
 6. The method as defined in one ofthe foregoing claims, wherein a ball whose diameter is greater than theinside diameter (b) of the passthrough orifice (5) of the high-pressurefuel reservoir to be shaped is used as the pressure element (10).
 7. Themethod as defined in one of the foregoing claims, wherein any drillingburr on the edge (7) formed by the continuous recess (2) and thepassthrough orifice (5) is removed before the pressure element (10) ispressed on.
 8. An apparatus for edge shaping in a high-pressure fuelreservoir which has an elongated tubular casing element (1) that isequipped in the longitudinal direction with a continuous recess (2),which forms the interior space of the high-pressure fuel reservoir andis open at at least one end, into which opens at least one passthroughorifice (5), configured as a bore, that together with the continuousrecess (2) forms a peripheral edge (7), characterized by an elongatedcasing-shaped guide element (11) that is insertable into the continuousrecess (2), having a recess (12) extending in the longitudinal directionof the guide element (11) and an orifice (16) branching off from therecess perpendicularly to said longitudinal direction; a pressureelement (10) mounted movably in the orifice (16); and an actuationelement (13), coacting with the pressure element (10) and arrangedshiftably in the recess (12), which is equipped at its end inserted intothe recess (12) with a surface segment (14) that is inclined at an angle(α) with respect to the longitudinal direction of the guide element (11)and is in contact against the pressure element (10), in which contextthe pressure element (10) can, by introduction of the actuation element(13) into the guide element (11), be impinged upon by a force, andconsequently pushes out with a surface portion (10 a) through theorifice (16) of the guide element in order to shape the edge (7) of thehigh-pressure fuel reservoir.
 9. The apparatus as defined in claim 8,wherein the actuation element (13) is arranged in slidingly shiftablefashion in the recess (12) of the guide element (11).
 10. The apparatusas defined in claim 8, wherein the end of the actuation element (13)inserted into the recess (12) of the guide element (11) is ofwedge-shaped configuration.
 11. The apparatus as defined in claim 8,wherein the orifice (16) is configured as a bore.
 12. The apparatus asdefined in claim 11, wherein the pressure element (10) makes contactagainst the inner wall of the orifice (16) with a slight lateralclearance.
 13. The apparatus as defined in one of claims 8 through 12,wherein the pressure element (10) is configured as a ball.
 14. Theapparatus as defined in claim 13, wherein the diameter of the ball (10)is greater than the inside diameter (b) of the passthrough orifice (5).